Fluororesin tubular product

ABSTRACT

There is described a fluororesin tubular product suitable for the surface layer of a fixing roll or a fixing belt for electrophotography. The tubular product of the present invention is a fluororesin tubular product formed by rolling, layering, and sticking a dense fluororesin film, wherein the number of rolling of the film is 2 or higher.

TECHNICAL FIELD

The present invention relates to a tubular product made of afluororesin, a fixing roll and a fixing belt using the tubular product,and a fixing apparatus using the fixing roll or the fixing belt.

BACKGROUND ART

In an image forming apparatus such as an electrophotographic copyingmachine or a laser beam printer, image formation is carried out by thesteps of: electrostatically charging a photosensitive drum uniformly;exposing to form an electrostatic latent image on the photosensitivedrum; developing to make the electrostatic latent image visible with atoner; transferring the toner on the photosensitive drum to a transfermaterial; fixing the toner on the transfer material; and cleaning thetoner remaining on the photosensitive drum after the transferring step.

In recent years, an electrophotographic image forming apparatus isrequired to improve the stability of the apparatus, assure highreliability, and save the cost of running for the purpose of makingeffective use of resources. As one of the measures to meet theserequirements, a study has been made to stop, by the use of a wax toner,the supply of a release oil to the surface of a fixing member such as afixing roll or a fixing belt; however, if the supply of a release oil isstopped, there occurs a problem that the surface layer of the fixingmember is quickly worn out by its contact both with paper edges and witha temperature sensor. Further, along with an improvement in the speed ofa copying machine and a laser printer, a load on the fixing member hasbeen increased, for which reason it has become difficult to assure along life of the fixing member.

Particularly, in a soft roll to be used for color image fixation, theeffect of a release agent on the prevention of wear is significant. If arelease agent is not supplied, scratching or wearing may take place insome cases on the surface layer of the soft roll only by printing onseveral hundred sheets, which layer is made of silicone rubber orfluororubber. Therefore, Journal of the Society of Electrophotography ofJapan, vol. 33, no. 1 (1994) and Japanese Patent Publication No.58-43740 proposes a fixing member produced by forming a silicone rubberelastic body as the outermost layer of a soft roll around a spindle andthen covering it with a PFA tube as a release layer having a wearresistance. However, the PFA tube is not satisfactory in the wearresistance required along with an improvement in the speed of anelectrophotographic apparatus and a tendency for oilless fixation inrecent years, and therefore, it is required to thicken the release layerof the surface layer for the purpose of prolonging the life of thefixing member.

On the other hand, to obtain a color fixed image of high quality, it isimportant for the surface of a fixing roll to follow the irregularitieson the surface of recording paper and to come in a uniform contact allover an unfixed toner image. If the fixing roll does not come in auniform contact, the degree of toner melting becomes uneven in theunfixed toner image, resulting in an uneven luster of the fixed imageand a deterioration of image quality. In general, fluororesins such asPFA have small elastic moduli as compared with silicone rubber andfluororubber, and the fluororesins are hardly strained, making itdifficult to follow the irregularities on the surface of recordingpaper. When the outermost layer is formed of a fluororesin, it isimportant to make the outermost layer as thin as possible so that theroll surface becomes easy to follow the irregularities on the surface ofrecording paper.

Further, for the purpose of carrying out the image fixation of a colorimage at a high speed and reducing electric power consumption to a lowlevel, it is preferred to decrease the heat capacity of a roll and theroll is required to have a high thermal conductivity. From such aviewpoint, it is also preferred to make the fluororesin layer as thin aspossible.

When a belt type fixing apparatus is used, which comprises a fixing belthaving a release layer formed on a belt made of a thin metal or a heatresistant resin such as polyimide and which further comprises arelatively long fixing nip part, the belt is required to have a lowerheat capacity and a higher thermal conductivity. Therefore, even when afluororesin layer is formed on such a fixing belt, it becomes importantto make the fluororesin layer as thin as possible.

However, in general, a fluororesin tube made of PFA or PTFE, which hasbeen used for the surface layer of a fixing roll or a fixing belt, isquite difficult to have a wall thickness of 25 μm or smaller from theviewpoint of forming. Therefore, for an improvement in image quality anda further energy saving, it is desired to develop a fluororesin releaselayer having a thickness of 25 μm or smaller. Further, with respect tothe inner diameter of a tube, it is usually impossible to produce a tubehaving an inner diameter of 50 mm or greater from the viewpoint offorming, and therefore, there is another problem that fluororesin tubescannot be applied to rolls of large diameter.

As described above, from the viewpoint of an improvement in imagequality and an energy saving, it is advantageous to decrease thethickness of the release surface layer of a fixing member, and on theother hand, from the viewpoint of assuring a long life of the surfacelayer, in the case of a release surface layer presently made available,it is required to increase the thickness of the release surface layer.In recent years, there has been required a release surface layer whichmeets both of these contradictory requirements.

With respect to a method for the production of a fluororesin tube, somemethods have been proposed so far; however, no methods meeting theabove-described requirements have been developed yet. For example, atube made of PTFE is particularly excellent in heat resistance andreleasing property among fluororesin tubes, and therefore, it is mostsuitable for the release surface layer; however, PTFE has a high meltviscosity, and unlike ordinary thermoplastic resins, it cannot be formedby melt extrusion, and therefore, in general, the formation of PTFE isusually carried out by a paste extrusion method in which a PTFE powderand a liquid lubricant such as naphtha or xylene are uniformly blendedand the thus obtained paste-like blend is extruded into a tubular shape,followed by extraction or drying to remove the liquid lubricant.However, when such a paste extrusion method is used, extrusion pressurebecomes high, if a tube is made to have a small wall thickness,resulting in an uneven distribution of the wall thickness and adeterioration of appearance, and therefore, there is a limit to make thewall thickness small.

Japanese Patent Laid-Open (Kokai) Publication No. 50-136367 discloses amethod for the production of a fluororesin tube of small wall thickness,comprising the steps of; applying a fluororesin coating material to ametal linear body and then baking the coating material to form a coatingon the linear body; extending the coated linear body at least until thefluororesin coating loses its adhesive property to the linear body; andthen pulling out the metal linear body. However, this method hasproblems that the evenness of wall thickness is hardly attained and thethus obtained tube is insufficient in wear resistance, strength, surfacesmoothness, and the like.

Japanese Patent Laid-Open (Kokai) Publication No. 4-296332 discloses afluororesin tube of small wall thickness, which is made of a modifiedPTFE containing 0.02% to 0.4% by weight of perfluoroalkyl vinyl ether orhexafluoropropylene and which has a value of 300 or higher as calculatedby dividing its inner diameter by its wall thickness. However, even withthe use of this method, as the tube has a smaller wall thickness, theformation of pin holes and a decrease in strength occur moresignificantly, and there are some problems that: it is substantiallydifficult to obtain a tube having a wall thickness of 40 μm or smaller;it is also difficult to produce a tube of large diameter having an innerdiameter of 60 mm or greater; and the heat resistance of the tube isdecreased by the modification of PTFE.

It is an objective of the present invention to provide a fluororesintubular product suitable for the surface layer of a fixing roll or afixing belt for electrophotography; a fixing roll and a fixing beltusing the tubular product as the surface layer; and a fixing apparatuscomprising the fixing roll and the fixing belt.

DISCLOSURE OF THE INVENTION

The present inventors have made an intensive study to solve theabove-described problems, and as a result, they have completed thepresent invention.

Thus the present invention provides a tubular product, a fixing roll anda fixing belt for electrophotography, and further provides a fixingapparatus, as described below.

(1) A fluororesin tubular product formed by rolling, layering, andsticking a dense fluororesin film, wherein the number of rolling of thefilm is 2 or greater.

(2) The fluororesin tubular product as set forth in (1) above, whereinthe film has a thickness of 20 μm or smaller.

(3) The fluororesin tubular product as set forth in (1) or (2) above,wherein the film is made of a dense polytetrafluoroethylene.

(4) The fluororesin tubular product as set forth in anyone of (1) to (3)above, wherein the tubular product has the maximum wall thickness of 2to 300 μm.

(5) The fluororesin tubular product as set forth in any one of (1) to(3) above, wherein the tubular product has the maximum wall thickness of2 to 90 μm.

(6) The fluororesin tubular product as set forth in any one of (1) to(5) above, wherein the tubular product has a surface roughness (Ra) of0.5 μm or lower.

(7) The fluororesin tubular product as set forth in any one of (1) to(6) above, wherein the tubular product has a tensile strength of 80N/mm² or higher.

(8) The fluororesin tubular product as set forth in any one of (1) to(7) above, wherein the tubular product has a light transmittance of 35%to 95% to light having a wavelength of 500 nm.

(9) The fluororesin tubular product as set forth in anyone of (1) to (8)above, wherein the tubular product has an inner surface subjected tosurface treatment for the improvement of adhesion property.

(10) A fixing roll comprising, as a surface layer, the fluororesintubular product as set forth in any one of (1) to (9) above, wherein thefilm has a thickness of 0.1 to 20 μm and the tubular product has themaximum wall thickness of 2 to 90 μm.

(11) A fixing belt comprising, as a surface layer, the fluororesintubular product as set forth in any one of (1) to (9) above, wherein thefilm has a thickness of 0.1 to 20 μm and the tubular product has themaximum wall thickness of 2 to 90 μm.

(12) A fixing apparatus comprising the fixing roll as set forth in (10)above.

(13) A fixing apparatus comprising the fixing belt as set forth in (11)above.

BRIEF DESCRIPTION OF DRAWING

FIG. 1 shows a drawing for the explanation of a method for spirallyrolling a belt-like fluororesin film on a spindle.

In FIG. 1, numeral 1 indicates a belt-like fluororesin film; numeral 2,a spindle; and numeral 3, a length corresponding to the distance ofrolling.

BEST MODE FOR CARRYING OUT THE INVENTION

The tubular product of the present invention is produced from afluororesin film with a dense structure as a material by rolling,layering, and sticking the fluororesin film. As the fluororesin film,there can be used a polytetrafluoroethylene (PTFE) film, atetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) film, atetrafluoroethylene-hexafluoropropylene copolymer (FEP) film, each ofwhich has a dense structure. With respect to the PFA and FEP, since theyare thermofusible, thin films each having a thickness of 10 μm orsmaller can easily be produced by an extrusion inflation method, acasting method, or the like. The thus obtained fluororesin film has adense structure and a high smoothness (Ra being 0.5 μm or lower). Withrespect to the PTFE, it is quite difficult to produce a film having athickness of 50 μm or smaller by a skiving method which is usually usedas a method for the production of a PTFE film. However, it is possibleto produce a dense thin film having a thickness of 10 μm or smaller by amethod for producing a stretched porous PTFE (ePTFE) film by hot press.Since the dense PTFE film produced by this method has been subjected toa stretching step, as compared with the PTFE film produced, for example,by a skiving method, the dense PTFE film has not only a high tensilestrength and a high wear resistance but also excellent properties suchas a high surface smoothness and a high light transmittance (a hightransparency).

As the fluororesin film to be used in the present invention, the densePTFE film produced by hot press of the ePTFE film is particularlypreferred because it is excellent in heat resistance, releasingproperty, strength, wear resistance, and the like.

The ePTFE film is obtained by removing a forming aid from a formed bodyof a paste obtained by mixing a PTFE fine powder and the forming aid;stretching the resulting formed body at a high temperature and a highspeed; and then, if necessary, baking the formed body. In the case ofuniaxial stretching, nodes (folded crystals) are formed like narrowislands at right angles to the direction of stretching, and fibrils(straight chain molecular bundles formed by loosening and pulling outthe folded crystals by the stretching) are oriented in the direction ofstretching just like a reed screen for connection between the nodes.Thus the film has a fibrous structure having voids in the spaces betweenthe neighboring fibrils or in the spaces defined by the fibrils and thenodes. In the case of biaxial stretching, fibrils are spread radially,and nodes exist like islands connecting the fibrils. Thus the film has afibrous structure just like a cobweb having a large number of spacesdefined by the fibrils and the nodes.

The ePTFE film, although it may be a uniaxially stretched ePTFE film ora biaxially stretched ePTFE film, is preferably a biaxially stretchedePTFE film. The biaxially stretched ePTFE film has a lower anisotropythan that of the uniaxially stretched ePTFE film because of stretchingin two different directions. The biaxially stretched eFTFE film canprovide a PTFE film having high values of strength both in the TDdirection (in the widthwise direction of the film) and in the MDdirection (in the lengthwise direction of the film).

The ePTFE film to be preferably used in the present invention has aporosity of 10% to 95%, preferably 40% to 90%.

The porosity is calculated by the following equation from the apparentdensity (ρ) measured according to the apparent density measurementmethod of JIS K 6885 (the same holds in the following).Porosity (%)=(2.2−ρ)/2.2×100   (a)

The stretch ratio in the TD direction is 100% to 5000%, preferably 100%to 2000%, whereas the stretch ratio in the MD direction is 100% to5000%, preferably 100% to 2000%. The ratio of values of tensile strengthin the lengthwise direction and in the widthwise direction of a densefilm obtained from the ePTFE film can be adjusted by the stretch ratiosin the TD direction and in the MD direction for the ePTFE film. Forexample, in the case of a dense film produced by using, as a materialfilm, an ePTFE film produced on the conditions that the stretch ratio is1200% in the TD direction and 600% in the MD direction, the tensilestrength of the dense film in the direction corresponding to the TDdirection of the ePTFE film becomes about two times as high as that ofthe dense film in the direction corresponding to the MD direction of thematerial film.

To produce a dense PTFE film as a material film for forming the tubularproduct of the present invention, at first, the ePTFE film is compressed(pressurized) at a temperature lower than the melting point in the firstcompression step to obtain a rolled film. At this time, the compressiontemperature is not particularly limited, if it is lower than the meltingpoint of PTFE; it is usually lower than the melting point by atemperature difference of 1° C. or more, preferably 100° C. or more. Ifthe compression temperature is higher than or equal to the meltingpoint, the dense film shrinks significantly. The compression conditionsare adjusted so that the thus obtained film has a porosity of 50% orlower, preferably 20% or lower, and more preferably 10% or lower. Thecompression pressure is usually 0.5 to 60 N/mm², preferably 1 to 50N/mm², in terms of surface pressure. The compression apparatus is notparticularly limited, if it can achieve the compression of a film.Preferably used are those which can compress a film by allowing the filmto pass between rolls or belts, such as a calender roll apparatus or abelt press apparatus. If a calender roll apparatus, or belt pressapparatus is used, air contained in the inside of an ePTFE film and airexisting between the layers of an ePTFE film can easily be pushed out tothe outside of the ePTFE film when the film is sandwiched between rollsor belts, so that there can be obtained a dense film free from voids(those which can be detected by surface observation (at a magnificationof 2000 times) with a scanning electron microscope (SEM); the same holdsin the following) and free from wrinkles.

The thickness of an ePTFE film, although it depends on the thickness ofthe desired film, the porosity of the ePTFE film, and the like, isusually 3 to 500 μm, preferably 5 to 200 μm.

The thickness is as measured with a {fraction (1/1000)} mm dialthickness gauge manufactured by Technolock on the condition that no loadis applied, except the spring load of the main body (the same holds inthe following).

The rolled film obtained in the first compression step is thencompressed (pressurized) at a temperature higher than or equal to themelting point of PTFE in the second compression step. At this time, thecompression temperature is not particularly limited, if it is higherthan or equal to the melting point of PTFE. The compression temperatureis usually higher than the melting point by 1° C. to 100° C., preferably20° C. to 80° C. The dense film can have an improved surface smoothnessby heating the ePTFE film at a temperature higher than or equal to themelting point. The compression temperature is preferably decreased to atemperature lower than the melting point at the time of releasing thepressure. If the pressure is released at a temperature higher than orequal to the melting point, the dense film shows significant shrinkageand easily causes wrinkling. The compression conditions are adjusted sothat the thus obtained dense film has a porosity of 10% or lower,preferably 1% or lower The compression pressure is usually 0.1 to 100N/mm², preferably about 1 to 30 N/mm², in terms of surface pressure. Thecompression apparatus is not particularly limited, if it can achievecompression while sandwiching a film. The use of a hot press apparatusor a belt press apparatus is preferred, which can apply heat andpressure to the film for a prescribed period of time.

The dense film can be produced by one press with an apparatus which canheat the ePTFE film at a temperature higher than or equal to the meltingpoint of PTFE while compressing the film and which can then cool thefilm to a temperature lower than or equal to the melting point of PTFEwhile maintaining the pressure. According to this method, even if theePTFE film is heated at a temperature higher than or equal to themelting point of PTFE from the starting of the compression, the ePTFEfilm is cooled to a temperature lower than the melting point of PTFEbefore the pressure applied to the ePTFE film is released, so that thethus obtained dense film can cause almost no shrinkage.

For example, if a belt press apparatus is used, a dense film with alittle shrinkage can be obtained by heating the ePTFE film at atemperature higher than or equal to the melting point of PTFE whilecompressing the film between belts, and then cooling the film to atemperature lower than the melting point. Moreover, this method ispreferred because the dense film can be produced in a continuous manner.

The PTFE film with a dense structure, which is obtained in such a manneras described above, may have a thickness appropriately selecteddepending on the applications thereof, although the thickness thereof isnot particularly limited. When the tubular product of the presentinvention is used for the surface layer of a fixing roll or fixing belt,the PTFE film has a thickness of 0.1 to 20 μm, preferably 1 to 10 μm,and the PTFE film has a surface roughness (Ra) (as measured according toJIS B 0601) of 0.1 μm or lower, preferably 0.05 μm or lower. The PTFEfilm has a high tensile strength (as measured according to JIS K 7127with a No. 2 specimen at a test speed of 50 mm/min and expressed interms of the values in the lengthwise direction and in the widthwisedirection), which is usually 80 N/mm² or higher, preferably 100 N/mm² orhigher.

The PTFE film has both a dense structure and a high surface smoothness,so that it has an excellent light transmitting property and has a highlight transmittance (as measured with a spectrophotometer, UV-240,manufactured by Shimadzu Corporation) of 80% or higher, particularly 90%or higher, to light having a wavelength of 500 nm, as measured in termsof transmittance to visible light having a wavelength of 500 nm.

When the first compression step is carried out, compression control maybe carried out in two or more steps for the purpose of decreasing thenumber of voids in the film to be produced. Further, in the secondcompression step, when a hot press apparatus is used, at the time ofcompression with a hot press plate, a heat resistant film having a highsurface smoothness may be inserted between the hot press plate and thefilm, followed by heating and compression. When a belt press apparatusis used, a heat resistant film having a high surface smoothness may beinserted between the belt made of a metal and the film, followed byheating and compression. At this time, a heat resistant polyimide filmor the like may be used as the heat resistant film. According to thismethod, the thus obtained dense PTFE film can have the same surfaceroughness (Ra) as that of the heat resistant film, which is effectivewhen the hot press plate or the belt made of a metal cannot have a highsurface smoothness.

According to the above-described method, a transparent PTFE thin filmhaving a thickness of 50 μm or smaller, which has been difficult toproduce by a skiving method, can easily be obtained. For example, anePTFE film having a porosity of 80% and a thickness of 40 μm iscompressed with a calender roll (at a roll temperature of 70° C.) tolower the porosity to 2% and the thickness to 12 μm, and the film isthen pressed with a belt press apparatus on the conditions that thepress plate temperature is 320° C. to 400° C., the pressure is 10.0N/mm², the feeding speed is 0.5 to 2.0 m/min, and the press time is 0.5to 10 minutes, to give a thin film having a porosity of 0% and athickness of 10 μm. Further, an ePTFE film having a porosity of 85% anda thickness of 9 μm is subjected to the same process to give a thin filmhaving a porosity of 0% and a thickness of 2 μm.

When heat press is carried out with a press plate in the secondcompression step, the surface roughness (Ra) of the PTFE film to beobtained in such a manner as described above depends on the surfaceroughness (Ra) of the plate, and when compression is carried out with ahot press plate for the rolled film obtained in the first compressionstep while the film is sandwiched between heat resistant films, thesurface roughness (Ra) of the PTFE film to be obtained depends mainly onthe surface roughness (Ra) of the heat resistant films. For example,when a press plate subjected to mirror finish treatment to have asurface roughness (Ra) of 0.1 μm or lower is used for the hot press, thesurface roughness (Ra) of the PTFE film to be obtained also becomes 0.1μm or lower. In a similar manner, when polyimide films each having ahigh surface smoothness (having an Ra of 0.01 μm) are used as releasefilms for sandwiching the rolled film obtained in the first compressionstep between the top and bottom release films, the surface roughness(Ra) of the PTFE film to be obtained also becomes about 0.01 μm

According to the above-described method, a transparent PTFE film can beobtained, whether thin or thick. In this method, an ePTFE film as amaterial film is compressed in the first compression step and thencompressed in the second compression step, both in the same manner asdescribed above. At this time, as the ePTFE film, an ePTFE film havingproperties similar to those off the ePTFE film described above andhaving a large thickness, for example, an ePTFE film having a thicknessof greater than 400 μm, usually 400 μm to 1 mm, may be used. Thematerial film may be a single film or a laminate film obtained bylaminating 2 to 100 films, preferably 2 to 20 films.

A PTFE film with a dense structure having a thickness of greater than 20μm and a high transparency can be obtained from such a thick ePTFE film.For example, a PTFE film having a porosity of 0% and a thickness of 50μm and having a high transparency and a luster in the surface thereofcan be obtained from a laminate film having a total thickness of 450 μm,which is produced by laminating three ePTFE films each having a porosityof 70% and a thickness of 150 μm. The PTFE film has a lighttransmittance of 80% or higher, preferably 85% or higher, and has aporosity of 10% or lower, preferably 2% or lower. The PTFE film has asurface roughness (Ra) of 0.1 μm or lower, preferably 0.05 μm or lower.Since the film is a PTFE film having a high transparency and a hightensile strength, it can be used for various applications, for example,protection films for construction materials, as a PTFE film having aheat resistance, a weather resistance, a chemical resistance, a wearresistance, and an excellent releasing property.

In the above-described method, the use of an ePTFE film having a hightensile, strength can provide a PTFE film having a high tensilestrength. For example, the use of an ePTFE film having a tensilestrength of 10 to 100 N/mm² can provide a PTFE film having a tensilestrength of 50 to 200 N/mm². A conventional PTFE cut film produced by askiving method usually has a tensile strength of 20 to 50 N/mm², and aconventional PTFE cast film has a tensile strength of about 20 to 40N/mm². As compared with these conventional PTFE films, the dense PTFEfilm obtained in such a manner as described above has an extremely hightensile strength.

The PTFE film will be further described in details. The film has aspecific gravity of 2.0 or higher, which is observed to have no voids,no pin holes, or no fibril structure by surface observation (at amagnification of 2000 times) with a scanning electron microscope (SEM).The film is a transparent film with a uniform appearance by visualobservation, which is observed to have no white opaque parts or no whitestripes caused by remaining voids, pin holes, or fibril structure.

The PTFE film has an extremely high transparency and an excellentdesigning property, whereas no conventional PTFE films have such a hightransparency.

The tubular product of the present invention can be produced by rolling,layering, and sticking the fluororesin film with a dense structure Inthe tubular product, the adhesion of rolled neighboring layers may becarried out by heat bonding or using an adhesive layer. The tubularproduct of the present invention can be produced by rolling afluororesin film in the prescribed number of rolling around a spindlemade of SUS, heat bonding the rolled neighboring layers of thefluororesin film by heating and baking at a temperature higher than orequal to the melting point of the fluororesin, and then removing thespindle made of SUS. The tubular product of the present invention canalso be produced by rolling a fluororesin film coated with an adhesiveon one surface thereof in the prescribed number of rolling around aspindle made of SUS, heating the film, if necessary, sticking the rolledneighboring layers of the fluororesin film, and then removing thespindle made of SUS. The method of rolling is not particularly limited,if it can layer the fluororesin film into a tubular shape; for example,a fluororesin film may be rolled like a Sushi-roll, or a belt-likefluororesin film may be rolled spirally.

FIG. 1 shows a drawing for the explanation of a method for rolling abelt-like fluororesin film spirally.

In FIG. 1, numeral 1 indicates a belt-like fluororesin film; numeral 2,is a spindle (a rod); and numeral 3, a length corresponding to thedistance of rolling on the spindle; the number of rolling is a valuecalculated by diving the length with the outer diameter of the spindle.

As shown in FIG. 1, belt-like fluororesin film 1, while slanting tospindle 2, is rolled around the spindle, so that a tubular product canbe obtained by spirally rolling the fluororesin film.

Further, a plurality of fluororesin films may be successively rolled.For example, a first fluororesin film is rolled in one or more lapsaround a spindle, and a second fluororesin film is rolled in one or morelaps further on the first fluororesin film around the spindle to give atubular product.

In such a tubular product, when an adhesive is used for sticking therolled neighboring layers, the adhesive may be applied to the innersurface of the fluororesin film. On the other hand, when the rolledneighboring layers are stuck by heat bonding, heating and baking may becarried out at a temperature higher than or equal to the melting pointof the fluororesin after the completion of the rolling.

When a tubular product is produced by rolling, layering, and sticking afluororesin film in such a manner as described above, the end of thefilm forming the outermost layer exists on the outer surface of thetubular product to be obtained, at which end of the film a step isformed. Further, if the position of the end at which the rolling of afilm is started (the leading end) is not completely corresponding to theposition of the end at which the rolling of the film is finished (theterminating end), a difference in the wall thickness of the tube iscaused at the ends of the film. For example, when a fluororesin film isrolled in the number of rolling of [n to n+1], there are formed tworegions, i.e., a region (a thinner portion) in which the wall thicknessof the tube consists of n layers and a region (a thicker portion) inwhich the wall thickness of the tube consists of n+1 layers, bothneighboring at the end of the fluororesin film in the outermost layerforming the outer surface of the tube. A difference in the wallthickness of the tube can be eliminated, if the position of the leadingend is completely corresponding to the position of the terminating end;however, in the practical production, a difference in position betweenthe leading end and the terminating end occurs because of variation,resulting in a difference in the wall thickness of the tube.

The study of the present inventors has found the following fact. When astep and a difference in thickness are significant, the obtained tube isunsatisfactory as the surface layer material for a fixing roll or afixing belt. In the case of the fixing roll or the fixing belt using thetube as the surface layer, a difference in surface temperature betweenthe thinner portion and the thicker portion becomes significant at thetime of a fixing step with an actual electrophotographic apparatus, anddifferences in color and in luster in a printed image become sosignificant as to be observed by visual observation. In contrast, if thenumber of rolling of the film is 2 or greater, preferably 3 or greater,a difference in temperature between the thinner portion and the thickerportion becomes insignificant, and differences in color and in luster ina printed image are reduced to such a level that they cannot be observedby visual observation.

In the present invention, the number of rolling is 2 or greater,preferably 3 or greater, of which upper limit is, although it is notparticularly limited, about 100.

Further, the trace of a step in the thickness of a fluororesin filmexisting at the end of the fluororesin film on the outer surface of atube occurs like a line on a printed image. In order to reduce theoccurrence of such a line trace, it is effective to make small thethickness of the fluororesin film. If the thickness of the fluororesinfilm is greater than 20 μm, the line trace clearly occur on a printedimage. On the other hand, if the thickness is 20 μm or smaller, usually15 μm or smaller, and particularly 10 μm or smaller, the line tracebecomes rather invisible. If the thickness of the film is 2 μm orsmaller, the line trace can hardly be observed by visual observation.When the film has a small thickness, the number of rolling is increasedto give a great wall thickness of the tube, so that a long life of thefixing material can be assured. For example, a PTFE film tube (having awall thickness of about 18 to 24 ∞m) in which the PTFE film has athickness of 6 μm and the number of rolling is 3.5, and a PTFE film tube(having a wall thickness of about 20.4 to 21.3 μm) in which the PTFEfilm has a thickness of 1.7 μm and the number of rolling is 12.5 haveapproximately the same durability. Smaller numbers of rolling of thefluororesin film are more advantageous from the viewpoint of productioncosts.

For example, a PTFE film produced by heat press of an ePTFE film canhave a thickness of 1 to 500 μm, in which the number of rolling can beincreased to about 100 laps. Therefore, the present invention canprovide various PTFE film tubes with optional combinations of thethickness of the PTFE film and the number of rolling.

When the tubular product of the present invention is used for thesurface layer of a fixing roll or a fixing belt, the thickness of afluororesin film to be rolled is 0.1 to 20 μm, preferably 1 to 10 m, andmore preferably 1.5 to 6 μm. The number of rolling of the film is 2 to50, preferably 3 to 30, and more preferably 3 to 20. The wall thicknessof the tube may appropriately be determined depending on the requiredproperties such as a wear resistance and a heat capacity, which arerequired on the basis of conditions such as a speed and a nip pressureof a fixing apparatus. The thickness of the thicker portion (the maximumwall thickness) is 2 to 90 μm, preferably 4 to 50 μm, and morepreferably 5 to 30 μm. If the maximum wall thickness is smaller than 2μm, no sufficient strength can be obtained and handling at the time ofproduction becomes difficult. If the maximum wall thickness is greaterthan 90 μm, it becomes difficult to follow the irregularities on thesurface of recording paper and the heat capacity of the fixing rollbecomes high.

The tube has a surface roughness (Ra) (as measured according to JIS B0601; the same holds in the following) of 0.5 μm or lower, preferably0.3 μm or lower, and more preferably 0.2 μm or lower. If the Ra is 0.5μm or higher, the releasing property of toner becomes insufficient andthe pressure to toner becomes uneven, resulting in a deterioration ofimage quality. Further, if voids (bubbles) remain in the tube wall, thetemperature of the roll surface becomes uneven, resulting in adeterioration of image quality. Therefore, as a tube to be used for thesurface layer of a fixing roll, tubes having both a high surfacesmoothness and a dense structure containing no voids are preferred, andas a result, tubes having a high light transmittance are desired.

When the fluororesin tubular product of the present invention is a densePTFE tubular product using a dense PTFE film produced by heat press ofan ePTFE film, the tubular product has a high tensile strength (asmeasured according to JIS K 7127 with a No. 2 specimen (the specimen isproduced by cutting the tube open) at a test speed of 50 mm/min andexpressed in terms of an average of the values in the lengthwisedirection and in the widthwise direction; the same holds in thefollowing), which is usually 80 N/mm² or higher, preferably 100 N/mm² orhigher. Further, the dense PTFE tubular product has both a densestructure and a high surface smoothness, so that the tubular product hasan excellent light transmitting property and has a light transmittanceof 35% to 95% (as measured with a spectrophotometer, UV-240,manufactured by Shimadzu Corporation) to light having a wavelength of500 nm, as measured in terms of transmittance to visible light having awavelength of 500 nm (the same holds in the following). If the lighttransmittance is lower than 35%, the dense PTEE film may contain voidsin some cases, and the presence of voids makes thermal conductivityuneven at the time of image fixation, causing uneven melting of toner.If the light transmittance is lower than 35%, Ra of the tube becomeshigher than 0.5 μm because of voids or wrinkles of the surface, andtherefore, the toner releasing property becomes insufficient or theapplication of pressure to the toner becomes uneven, resulting in adeterioration of image quality.

The tubular product of the present invention is preferably used for thesurface layer material of a fixing roll or a fixing belt, as describedabove; however, it is not limited to these applications and it can finduse in various applications, for example, a guiding tube of anendoscope, a catheter, a gas-liquid separation membrane, an insulatingcable coating material, a hose, an artificial blood vessel, an opticalfiber for pneumatic process, a liquid transfusion pipe, and the like.When the tubular product of the present invention is used forapplications other than fixing rolls or fixing belts, the wall thicknessthereof is not particularly limited and appropriately selected dependingon the applications. In general, the tubular product has a wallthickness of 2 to 300 μm, preferably 5 to 100 μm, in terms of themaximum wall thickness. The inner diameter of the tubular product isalso appropriately determined depending on the applications, which isusually 5 to 150 mm, preferably 20 to 70 mm.

When the tubular product of the present invention is used for thesurface layer material of a fixing roll, the inner diameter thereof isusually about 20 to 70 mm, and the maximum wall thickness thereof is 2to 90 μm, preferably 4 to 50 μm, and more preferably 5 to 30 μm.

When the tubular product of the present invention is used for thesurface layer material of a fixing belt, the inner diameter thereof isusually about 30 to 150 mm, and the maximum wall thickness thereof is 2to 90 μm, preferably 4 to 50 μm, and more preferably 5 to 30 μm.

When a tubular product made of a fluororesin film with a dense structureis produced according to the present invention, the fluororesin filmwith a dense structure is rolled, layered, and stuck into a tubularshape. For example, in the case of a dense PTFE film, as a preferredmethod for rolling, layering, and sticking the PTFE film into a tubularshape, there is a method by rolling the PTFE film in a plurality of lapsaround a spindle made of a metal, heating the rolled product in an ovenat a temperature higher than or equal to the melting point of PTFE,cooling the rolled product in air, and then removing the PTFE filmsurrounding the spindle made of a metal. This method makes it possibleto obtain a dense PTFE tube with a layer structure like a Sushi-roll. Atthis time, the surface of the spindle may previously be roughened bysand blast processing or the like in order to improve the releasingproperty from the PTFE tube. The thus obtained PTFE tube is free fromthe entrainment of air in neighboring layers, so that the respectivelayers are completely stuck to the next layers, of which adhesionstrength is as high as a cohesion failure occurs in the PTFE film at thetime of delamination. In addition, one surface or both surfaces of thePTFE film may previously be subjected to conventionally known surfacetreatment such as corona discharge treatment, chemical etchingtreatment, or excimer laser treatment, so that a sufficiently highinterlayer adhesion strength can be obtained by heating for a shorterperiod of time and a heat deterioration of the PTFE film can besuppressed. When an ordinary plastic film is formed into a tubular shapein the same manner, there occur problems that some amount of air isentrained between the layers of the rolled film to make interlayeradhesion uneven and gaps remain between the layers after heat treatment.Further, if an ordinary thermofusible plastic is heated to a temperaturehigher than or equal to the melting point, the plastic is melted andfluidized, so that the thickness thereof easily becomes uneven and thesurface thereof is roughened because of swelling by heat, and so thatthe plastic adheres to the spindle made of a metal and becomes difficultto remove. Therefore, as compared with PFA and FEP, both of which arethermofusible fluororesins, PTFE can easily be formed. A PTFE film hastwo characteristics: (1) the film is hardly fluidized even at a meltingpoint of PTFE; and (2) the film has a gas permeability. Therefore, thepresent inventors have found that if a PTFE film is rolled around aspindle made of a metal and heated to a temperature higher than or equalto the melting point of PTFE, air entrained in the film layers can bereleased without causing an unevenness of thickness or an unevenness ofadhesion between the neighboring film layers and that a tube in whichthe respective layers are completely stuck to one another can easily beformed.

The dense PTFE tubular product of the present invention can be subjectedto conventionally known surface treatment on the inner surface thereof,such as corona discharge treatment, chemical etching treatment, andexcimer laser treatment, for the purpose of improving the adhesionproperty of the inner surface of the PTFE tube. For example, afterchemical etching with Tetra H (manufactured by Junkosha Inc.), thetubular product may be used for producing a fixing roll or a fixing belthaving the surface layer of a PTFE tube according to a conventionalmethod. The tube surface subjected to chemical etching may cause acoloration or give a fine cracking structure in some cases; however,this is no problem for use as the surface layer of a fixing roll.

Two directions are available as a direction for assembling thefluororesin tube of the present invention on a fixing roll to thedirection of rotation of a fixing roll: a direction of inserting thefluororesin tube into a nip part from the thicker portion to the thinnerportion in this order; and a direction of inserting the fluororesin tubeinto a nip part from the thinner portion to the thicker portion in thisorder. With respect to seam line traces to be formed on a printed image,or differences in color and in luster corresponding to the thinnerportion and the thicker portion of the surface layer of the fixing roll,they occur at approximately the same levels in both directions ofinsertion; however, the direction of insertion into a nip part from thethicker portion to the thinner portion in this order is preferredbecause of an advantageous effect on the tearing of the surface layer.

EXAMPLES

The present invention will hereinafter be further described in detailsby way of Examples.

Example 1

A dense PTFE film (10 μm in thickness, 550 mm in width×175 mm in length)subjected to corona discharge treatment on one surface thereof wasrolled, like a Sushi-roll, in 2.1 laps around a spindle made of SUS(26.5 mm in outer diameter and 500 mm in length) in such a manner thatthe corona treated surface was in the inner side. At this time, the filmwas rolled in the lengthwise direction, and the end of the film wasfixed with ring-like stoppers so that the film did not shrink in theaxial direction of the spindle made of SUS. The film was then baked at400° C. in an oven for 30 minutes and cooled in air, after which thestoppers were detached and a PTFE tubular product was removed from thespindle made of SUS to obtain a dense PTFE tubular product having themaximum wall thickness of 30 μm (20 μm in the thickness of the two-layerportion and 30 μm in the thickness of the three-layer portion) and aninner diameter of 26.5 mm. The dense PTFE tubular product had an Ra of0.340 μm, a tensile strength of 120 N/mm², and a light transmittance of75% to light having a wavelength of 500 nm.

Example 2

A dense PTFE tubular product having the maximum wall thickness of 28 μmand an inner diameter of 26.5 mm was obtained in the same manner asdescribed in Example 1, except that a dense PTFE film (4 μm in thicknessand 550 mm in width×540 mm in length) subjected to corona dischargetreatment on one surface thereof was rolled, like a Sushi-roll, in 6.5laps around a spindle made of SUS (26.5 mm in outer diameter and 500 mmin length) in such a manner that the corona treated surface was in theinner side. The dense PTFE tubular product had an Ra of 0.200 μm, atensile strength of 130 N/mm², and a light transmittance of 80% to lighthaving a wavelength of 500 nm.

Example 3

A dense PTFE tubular product having the maximum wall thickness of 27 μmand an inner diameter of 26.5 mm was obtained in the same manner asdescribed in Example 1, except that a dense PTFE film (1.7 μm inthickness and 550 mm in width×1290 mm in length) subjected to coronadischarge treatment on one surface thereof was rolled, like aSushi-roll, in 15.5 laps around a spindle made of SUS (26.5 mm in outerdiameter and 500 mm in length) in such a manner that the corona treatedsurface was in the inner side. The dense PTFE tubular product had an Raof 0.080 μm, a tensile strength of 150 N/mm², and a light transmittanceof 80% to light having a wavelength of 500 nm.

Example 4

A dense PTFE tubular product having the maximum wall thickness of 7 μmand an inner diameter of 26.5 mm was obtained in the same manner asdescribed in Example 1, except that a dense PTFE film (1.7 μm inthickness and 550 mm in width×291 mm in length) subjected to coronadischarge treatment on one surface thereof was rolled, like aSushi-roll, in 3.5 laps around a spindle made of SUS (26.5 mm in outerdiameter and 500 mm in length) in such a manner that the corona treatedsurface was in the inner side. The dense PTFE tubular product had an Raof 0.080 μm, a tensile strength of 140 N/mm², and a light transmittanceof 88% to light having a wavelength of 500 nm.

Example 5

A dense PTFE tubular product having the maximum wall thickness of 27 μmand an inner diameter of 45 mm was obtained in the same manner asdescribed in Example 1, except that a dense PTFE film (1.7 μm inthickness and 550 mm in width×2190 mm in length) subjected to coronadischarge treatment on one surface thereof was rolled, like aSushi-roll, in 15.5 laps around a spindle made of SUS (45 mm in outerdiameter and 500 mm in length) in such a manner that the corona treatedsurface was in the inner side The dense PTFE tubular product had an Raof 0.100 μm, a tensile strength of 150 N/mm², and a light transmittanceof 80% to light having a wavelength of 500 nm.

Example 6

A dense PTFE tubular product having the maximum wall thickness of 7 μmand an inner diameter of 100 mm was obtained in the same manner asdescribed in Example 1, except that a dense PTFE film (1.7 μm inthickness and 777 mm in width×800 mm in length) subjected to coronadischarge treatment on one surface thereof was rolled in 3.5 laps arounda spindle made of SUS (100 mm in outer diameter and 500 mm in length) insuch a manner that the spindle axis and the lengthwise direction of thefilm were kept at 45° to each other. The dense PTFE tubular product hadan Ra of 0.250 μm, a tensile strength of 140 N/mm², and a lighttransmittance of 88% to light having a wavelength of 500 nm.

Example 7

The PTFE tube produced in Example 1 was impregnated on the inner surfacethereof with a Na/naphthalene complex salt solution (trade name: TetraH, manufactured by Junkosha Inc.) at 25° C., and then immersed inmethanol, water, and methanol in this order for 10 seconds each, anddried by blowing air to the inner and outer surfaces thereof. A primer(trade name: DY 39-051, manufactured by Toray Dow Corning Co., Ltd.) wasapplied to the thus treated inner surface of the tube, which was thenattached to an inner wall of a mold for forming a roll having an innerdiameter of 27.5 mm. An aluminum spindle (25 mm in outer diameter and320 mm in length) was held in the center of the mold. Silicone rubberwas injected between the tube and the aluminum spindle, and thenthermally hardened at 150° C. for 30 minutes, followed by secondaryvulcanization at 200° C. for 4 hours, to obtain a fixing roll having adense PTFE film as the surface layer thereof.

Example 8

A fixing roll having a dense PTFE film as the surface layer thereof wasobtained in the same manner as described in Example 7, except that thePTFE tube produced in Example 2 was used.

Example 9

A fixing roll having a dense PTFE film as the surface layer thereof wasobtained in the same manner as described in Example 7, except that thePTFE tube produced in Example 3 was used.

Example 10

A fixing roll having a dense PTFE film as the surface layer thereof wasobtained in the same manner as described in Example 7, except that thePTFE tube produced in Example 4 was used.

Comparative Example 1

A fixing roll was obtained in the same manner as described in Example 7,except that a PFA tube (STM, manufactured by Gunze Ltd.) having a wallthickness of 30 μm was used.

Comparative Example 2

A dense PTFE tubular product having the maximum wall thickness of 20 μmand an inner diameter of 26.5 mm was obtained in the same manner asdescribed in Example 1, except that a dense PTFE film (10 μm inthickness and 550 mm in width×125 mm in length) subjected to coronadischarge treatment on one surface thereof was rolled in 1.5 laps arounda spindle made of SUS (26.5 mm in outer diameter and 500 mm in length)in such a manner that the corona treated surface was in the inner side.The thus obtained tubular product was used to produce a fixing rollhaving the dense PTFE film as the surface layer thereof in the samemanner as described in Example 7.

Each of the fixing rolls obtained in Examples 7 to 10 and ComparativeExamples 1 and 2 was mounted in an electrophotographic printer(DocuPrint C2220, manufactured by Fuji Xerox Co., Ltd.) and paperfeeding evaluation was carried out to compare the occurrence of tearingof the surface layer. The results are shown in Table 1. As can be seen,when the dense PTFE tubular products obtained in Examples according tothe present invention were used for the surface layers of the fixingrolls, a remarkably high wear resistance was obtained as compared withthat of Comparative Example 1 using a conventional PFA tube. TABLE 1Comp. Comp. Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 1 Ex. 2 Number (K) of220 >300 >300 150 80 180 paper sheets fed until surface layer was tornout.

Each of the fixing rolls obtained in Examples 7 to 10 and ComparativeExample 2 was mounted in an electrophotographic printer (DocuPrintC2220, manufactured by Fuji Xerox Co., Ltd.) and image output wascarried out to compare the trace (in a line-like state) at the film endof the surface layer appearing on the image. The results are shown inTable 2. As can be seen, when the dense PTFE tubular products obtainedin Examples according to the present invention were used for the surfacelayers of the fixing rolls, the trace at the film end of the surfacelayer was more hardly formed, if the dense PTFE film used for rollingand layering had a smaller thickness. TABLE 2 Comp. Ex. 7 Ex. 8 Ex. 9Ex. 10 Ex. 2 Trace at Appearing slightly Not Not Appearing film end ofin appearing appearing appearing in surface line- line- layer like likestate state

Each of the fixing rolls obtained in Examples 7 to 10 and ComparativeExample 2 was mounted in an electrophotographic printer (DocuPrintC2220, manufactured by Fuji Xerox Co., Ltd.) and image output wascarried out to evaluate a difference in luster between the portionsdivided by the trace at the film end of the surface layer appearing onthe image. The results are shown in Table 3. As can be seen, when thedense PTFE tubular products obtained in Examples according to thepresent invention were used for the surface layers of the fixing rolls,a difference in luster was caused between the portions divided by thetrace at the film end of the surface layer, if the number of rolling ofthe dense PTFE film used for rolling and layering was 1.5. This isbecause if the number of rolling was smaller than 2, a difference in thewall thickness of the dense PTFE tubular product became significant,resulting in an uneven degree of toner melting. TABLE 3 Comp. Ex. 7 Ex.8 Ex. 9 Ex. 10 Ex. 2 Difference No No No No Difference in differencedifference difference difference in luster in in in in luster betweenluster luster luster luster portions divided by trace of film end ofsurface layer

Each of the fixing rolls obtained in Examples 7 to 10 and ComparativeExamples 1 and 2 was mounted in an electrophotographic printer(DocuPrint C2220, manufactured by Fuji Xerox Co., Ltd.) and image outputwas carried out to compare the unevenness of luster in a solid image.The results are shown in Table 4. As can be seen, if the tubular productused for the surface layer of the fixing roll had a small wallthickness, the luster in the solid image hardly became uneven. TABLE 4Comp. Comp. Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 1 Ex. 2 Unevenness UnevenUneven Uneven Even Uneven Uneven of luster luster luster luster lusterluster luster in solid image

As describe above, the present invention makes it possible to provide atubular product suitable for a fixing member for electrophotographywhich has a high durability and which can attain a high image qualityand a reduction in energy consumption, the tubular product having beendifficult to obtain in the prior art.

1. A fluororesin tubular product formed by rolling, layering, andsticking a dense fluororesin film, wherein the number of rolling of thefilm is 2 or greater.
 2. The fluororesin tubular product according toclaim 1, wherein the film has a thickness of 20 μm or smaller.
 3. Thefluororesin tubular product according to claim 1, wherein the film ismade of a dense polytetrafluoroethylene.
 4. The fluororesin tubularproduct according to claim 1, wherein the tubular product has a maximumwall thickness of 2 to 300 μm.
 5. The fluororesin tubular productaccording to claim 1, wherein the tubular product has a maximum wallthickness of 2 to 90 μm.
 6. The fluororesin tubular product according toclaim 1, wherein the tubular product has a surface roughness (Ra) of 0.5μm or lower.
 7. The fluororesin tubular product according to claim 1,wherein the tubular product has a tensile strength of 80 N/mm² orhigher.
 8. The fluororesin tubular product according to claim 1, whereinthe tubular product has a light transmittance of 35% to 95% to lighthaving a wavelength of 500 nm.
 9. The fluororesin tubular productaccording to claim 1, wherein the tubular product has an inner surfacesubjected to surface treatment for improvement of adhesion property. 10.A fixing roll comprising, as a surface layer, the fluororesin tubularproduct according to claim 1, wherein the film has a thickness of 0.1 to20 μm and the tubular product has a maximum wall thickness of 2 to 90μm.
 11. A fixing belt comprising, as a surface layer, the fluororesintubular product according to claim 1, wherein the film has a thicknessof 0.1 to 20 μm and the tubular product has a maximum wall thickness of2 to 90 μm.
 12. A fixing apparatus comprising the fixing roll accordingto claim
 10. 13. A fixing apparatus comprising the fixing belt accordingto claim
 11. 14. The fluororesin tubular product according to claim 2,wherein the film is made of a dense polytetrafluoroethylene.
 15. Thefluororesin tubular product according to claim 2, wherein the tubularproduct has a maximum wall thickness of 2 to 300 μm.
 16. The fluororesintubular product according to claim 3, wherein the tubular product has amaximum wall thickness of 2 to 300 μm.
 17. The fluororesin tubularproduct according to claim 2, wherein the tubular product has a maximumwall thickness of 2 to 90 μm.
 18. The fluororesin tubular productaccording to claim 3, wherein the tubular product has a maximum wallthickness of 2 to 90 μm.
 19. The fluororesin tubular product accordingto claim 2, wherein the tubular product has a surface roughness (Ra) of0.5 μm or lower.
 20. The fluororesin tubular product according to claim3, wherein the tubular product has a surface roughness (Ra) of 0.5 μm orlower.
 21. The fluororesin tubular product according to claim 4, whereinthe tubular product has a surface roughness (Ra) of 0.5 μm or lower. 22.The fluororesin tubular product according to claim 5, wherein thetubular product has a surface roughness (Ra) of 0.5 μm or lower.
 23. Thefluororesin tubular product according to claim 2, wherein the tubularproduct has a tensile strength of 80 N/mm² or higher.
 24. Thefluororesin tubular product according to claim 3, wherein the tubularproduct has a tensile strength of 80 N/mm² or higher.
 25. Thefluororesin tubular product according to claim 4, wherein the tubularproduct has a tensile strength of 80 N/mm² or higher.
 26. Thefluororesin tubular product according to claim 5, wherein the tubularproduct has a tensile strength of 80 N/mm² or higher.
 27. Thefluororesin tubular product according to claim 6, wherein the tubularproduct has a tensile strength of 80 N/mm² or higher.
 28. Thefluororesin tubular product according to claim 2, wherein the tubularproduct has a light transmittance of 35% to 95% to light having awavelength of 500 nm.
 29. The fluororesin tubular product according toclaim 3, wherein the tubular product has a light transmittance of 35% to95% to light having a wavelength of 500 nm.
 30. The fluororesin tubularproduct according to claim 4, wherein the tubular product has a lighttransmittance of 35% to 95% to light having a wavelength of 500 nm. 31.The fluororesin tubular product according to claim 5, wherein thetubular product has a light transmittance of 35% to 95% to light havinga wavelength of 500 nm.
 32. The fluororesin tubular product according toclaim 6, wherein the tubular product has a light transmittance of 35% to95% to light having a wavelength of 500 nm.
 33. The fluororesin tubularproduct according to claim 7, wherein the tubular product has a lighttransmittance of 35% to 95% to light having a wavelength of 500 nm. 34.The fluororesin tubular product according to claim 2, wherein thetubular product has an inner surface subjected to surface treatment forimprovement of adhesion property.
 35. The fluororesin tubular productaccording to claim 3, wherein the tubular product has an inner surfacesubjected to surface treatment for improvement of adhesion property. 36.The fluororesin tubular product according to claim 4, wherein thetubular product has an inner surface subjected to surface treatment forimprovement of adhesion property.
 37. The fluororesin tubular productaccording to claim 5, wherein the tubular product has an inner surfacesubjected to surface treatment for improvement of adhesion property. 38.The fluororesin tubular product according to claim 6, wherein thetubular product has an inner surface subjected to surface treatment forimprovement of adhesion property.
 39. The fluororesin tubular productaccording to claim 7, wherein the tubular product has an inner surfacesubjected to surface treatment for improvement of adhesion property. 40.The fluororesin tubular product according to claim 8, wherein thetubular product has an inner surface subjected to surface treatment forimprovement of adhesion property.
 41. A fixing roll comprising, as asurface layer, the fluororesin tubular product according to claim 2,wherein the film has a thickness of 0.1 to 20 μm and the tubular producthas a maximum wall thickness of 2 to 90 μm.
 42. A fixing rollcomprising, as a surface layer, the fluororesin tubular productaccording to claim 3, wherein the film has a thickness of 0.1 to 20 μmand the tubular product has a maximum wall thickness of 2 to 90 μm. 43.A fixing roll comprising, as a surface layer, the fluororesin tubularproduct according to claim 4, wherein the film has a thickness of 0.1 to20 μm and the tubular product has a maximum wall thickness of 2 to 90μm.
 44. A fixing roll comprising, as a surface layer, the fluororesintubular product according to claim 5, wherein the film has a thicknessof 0.1 to 20 μm and the tubular product has a maximum wall thickness of2 to 90 μm.
 45. A fixing roll comprising, as a surface layer, thefluororesin tubular product according to claim 6, wherein the film has athickness of 0.1 to 20 μm and the tubular product has a maximum wallthickness of 2 to 90 μm.
 46. A fixing roll comprising, as a surfacelayer, the fluororesin tubular product according to claim 7, wherein thefilm has a thickness of 0.1 to 20 μm and the tubular product has amaximum wall thickness of 2 to 90 μm.
 47. A fixing roll comprising, as asurface layer, the fluororesin tubular product according to claim 8,wherein the film has a thickness of 0.1 to 20 μm and the tubular producthas a maximum wall thickness of 2 to 90 μm.
 48. A fixing rollcomprising, as a surface layer, the fluororesin tubular productaccording to claim 9, wherein the film has a thickness of 0.1 to 20 μmand the tubular product has a maximum wall thickness of 2 to 90 μm. 49.A fixing belt comprising, as a surface layer, the fluororesin tubularproduct according to claim 2, wherein the film has a thickness of 0.1 to20 μm and the tubular product has a maximum wall thickness of 2 to 90μm.
 50. A fixing belt comprising, as a surface layer, the fluororesintubular product according to claim 3, wherein the film has a thicknessof 0.1 to 20 μm and the tubular product has a maximum wall thickness of2 to 90 μm.
 51. A fixing belt comprising, as a surface layer, thefluororesin tubular product according to claim 4, wherein the film has athickness of 0.1 to 20 μm and the tubular product has a maximum wallthickness of 2 to 90 μm.
 52. A fixing belt comprising, as a surfacelayer, the fluororesin tubular product according to claim 5, wherein thefilm has a thickness of 0.1 to 20 μm and the tubular product has amaximum wall thickness of 2 to 90 μm.
 53. A fixing belt comprising, as asurface layer, the fluororesin tubular product according to claim 6,wherein the film has a thickness of 0.1 to 20 μm and the tubular producthas a maximum wall thickness of 2 to 90 μm.
 54. A fixing beltcomprising, as a surface layer, the fluororesin tubular productaccording to claim 7, wherein the film has a thickness of 0.1 to 20 μmand the tubular product has a maximum wall thickness of 2 to 90 μm. 55.A fixing belt comprising, as a surface layer, the fluororesin tubularproduct according to claim 8, wherein the film has a thickness of 0.1 to20 μm and the tubular product has a maximum wall thickness of 2 to 90μm.
 56. A fixing belt comprising, as a surface layer, the fluororesintubular product according to claim 9, wherein the film has a thicknessof 0.1 to 20 μm and the tubular product has a maximum wall thickness of2 to 90 μm.